Lower Unit Oil??

turtle1173

Chief Petty Officer
Joined
Nov 29, 2001
Messages
437
I had a question regarding regarding Lower Units. I have a 1975 55 HP Chrysler. To my knowledge the lower unit oil has never been changed. When I change this oil should I expect and problems? Will it be real thick or thin? I'm just trying to anticipate any problems before I take out the screws. Any advice?<br /><br /> I've heard the lower units be compared to the rear end of a car. Is this a correct illustration? Is the oil in the lower unit similar to the oil that would be in the differential? I'm just trying to get a better idea at how all of this works. I'm still quite the novice :D <br /><br />Thanks,<br /><br />Shane
 

Yepblaze

Lieutenant Commander
Joined
Jun 1, 2001
Messages
1,686
Re: Lower Unit Oil??

It should be just like the gear oil in a rear end. Remove the drain plug and also the vent plug.<br /><br />If it has been sitting for more than a week or two, you might see a few drops of water come out first. More than a few drops of water can indicate need for attention. Like seals replacement. If rusty water comes out that is bad. <br /><br />It is usually suggested here to replace the washers on the plugs as they sometimes leak water in if they don't seal well upon reassembly.<br /><br />I usualy use a good grade 80-90wt gear oil and buy a couple of quarts. With two quarts on hand I can cut the tip off one bottle and push it into the lower drain hole. Then squeeze till you can't squeeze any more. Now remove the bottle while putting your finger on the hole while your assistant refills the bottle from the second quart. Then squeeze in some more till it runs out the top vent hole.
 

Pursuit2150

Chief Petty Officer
Joined
Dec 3, 2001
Messages
553
Re: Lower Unit Oil??

There are 2 key indicators when replacing lower unit oil : If it is grey in color you have water in the system, the next is to check for small particals of metal, which indicates some gear mesh problems. You should be changing the lower unit lube at least 1 time per season.
 

Grizzly

Petty Officer 2nd Class
Joined
Dec 13, 2001
Messages
106
Re: Lower Unit Oil??

SHANE, I bought a little gadget that makes the job a little easier with less mess. One end replaces the cap on your bottle of gear oil and has a "finger pump" similar to a bottle of hand soap. A short hose connects to a fitting which is threaded to fit the bottom hole. Remember to remove the top plug after you get the fitting tight and you're in business. To add a 2nd bottle, just switch the pump to the new bottle and continue. A good investment for about 5 bucks at Walmart or K-mart. Have a great day. -G. :)
 

its-a-sweater

Seaman
Joined
Dec 29, 2001
Messages
60
Re: Lower Unit Oil??

It is alot like a car rear axle meaning hypoid. I would not use an automotive lube in them though. Use a marine 80 to 90 weight gear lube.
 

Trent

Captain
Joined
Nov 17, 2001
Messages
3,333
Re: Lower Unit Oil??

Their are three API service categories for gear oils.<br /><br />API-GL1, API-GL4, API-GL5.<br /><br />Most outboard manufactures recommend API-GL5 gear oil for their lower units. API-GL5 gear lubricants are for both mechanical shift units calling for type B gear oil and electrical shift mechanisms calling for type C gear oil (only the viscosity value will be different for each application)
 

Rex

Chief Petty Officer
Joined
Aug 12, 2001
Messages
424
Re: Lower Unit Oil??

I KNOW ONE THING IF THE LUBE COME OUT LET'S<br />SAY NOT THE BEST I WOULD CHANGE THE LUBE<br />EACH TIME FOR ABOUT 3 RUNS. THEN IF IT LOOKS<br />BAD LIKE MILK THEN YOU KNOW YOU GOT BAD SEAL<br />I KNOW TRENT AND I DO NOT AGREE ON THIS BUT<br />YOU COULD SPRAY THE SEAL DOWN WITH BRAKE<br />FUILD TO SOFTING THEM UP. IF THEY GET A SOFT<br />THEY MIGHT START TO SEAL FOR YOU.<br />BUT CHANGE THE LUBE EVERY TIME FOR THE FIRST<br />2 OR 3 BEFORE IT COST YOU ABOUT $300.00<br />TO WORK ON THE LOWER UNIT.<br />I HOPE YOUR NOT MAD TRENT.<br />GOOD LUCK<br />REX A HUBBLE
 

Trent

Captain
Joined
Nov 17, 2001
Messages
3,333
Re: Lower Unit Oil??

Rex.. Iv never been mad at you. I just disagreed with you on the brake fluid thing.. If it works for you, go for it!! But I will just replace the seals. <br /><br />But what the heck do I know :(
 
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